The last month of the big league season began on a scintillating Sunday and provided enough drama to carry us through a long weekend and straight into Monday's new series lid-lifters and the official homestretch of the pennant races.

The first day of September gave us the traditional roster expansions; an amazing comeback in the East; a big series sweep out West; yet another Dodgers win highlighted by good pitching and Yasiel Puig's heroics; stellar pitching performances when they matter the most; and one more day of increased confusion at the top of the wide-open National League Central.

The Pulse of the Postseason was reverberating all over the parks of the American and National Leagues, and perhaps no louder than in the Bronx during Sunday's early games. The Yankees were enjoying a 3-0 lead on one of the teams they are fighting to stay in the AL Wild Card race, the Orioles, until Baltimore erupted for seven runs in the seventh inning to turn it into a 7-3 laugher and keep hope alive for a big run in September.

J.J. Hardy and Adam Jones punctuated the rally by each hitting a three-run home run, and Jones took to Twitter shortly after the game to express the workmanlike attitude the team is sticking to as it tries to pull off the improbable for a second consecutive year.

Lets grind and do what we need to for ourselves. We control US no one else. Lets continue the mission #StayHungry

While Jones preferred a low-key form of celebration, the Oakland A's had their own reason to be pumped. They finished off a weekend sweep of the contending Rays by beating Tampa Bay, 5-1, on the strength of an excellent start by A.J. Griffin and home runs by Coco Crisp and Stephen Vogt.

The A's might still be behind the Rangers in the AL West, but they are only a game behind, and they did what they had to do against Tampa Bay and now meet Texas in a crucial series that begins Monday.

"I don't want the [Wild Card] game," A's manager Bob Melvin said. "You try not to get too caught up in it, but you can't help it. Everybody is, and once you get into September, it feels like the finish-line is in sight."

With Sunday's win, the A's are still comfortably ahead in the Wild Card standings, as Major League Baseball's official Twitter account highlighted:

In the AL Central, the Royals need to win as many games as they can to stay in the race, and they got everything they wanted Sunday in a 5-0 victory over Toronto in which starter James Shields lived up to his "Big Game" nickname, tossing seven scoreless innings and striking out nine.

And in the NL Central, the Cardinals made the Majors' most tightly contested division even more intriguing by pasting the Pirates in Pittsburgh to the tune of a 7-2 victory to pull even with the Bucs for the division lead. With the win, St. Louis improved to 6-4 with a week remaining in a 17-game stretch against postseason contenders Atlanta, Cincinnati and Pittsburgh. The Cardinals will get one more look at the Pirates next weekend during a three-game series, but even more imminent is the series against Cincinnati that begins Monday.

The Reds, who are still only 3 1/2 games back in the division, are ready and waiting, as the team's Twitter account showed:

Not to be outdone -- and is he ever? -- Puig homered to break a sixth-inning tie against the Padres and help surging starter Zack Greinke to a victory as the Dodgers continued to roll. Hours later, the Cuban import proved he is indeed human by showing via Twitter and Instagram that he has to travel from city to city just like his teammates. He does not have a cape and the ability to fly, although he does have some pretty sweet big league threads.

Elsewhere, Sunday gave us a nifty series sweep by the first-place Red Sox and a must-win for still-hanging-in-there Cleveland over the AL Central-leading Tigers, who prevailed on the strength of a ninth-inning grand slam by Mike Aviles.

"We've got to beat everybody right now," Indians reliever Cody Allen said. "We put ourselves in the position where every game means a lot. It doesn't matter if it's these guys, the Braves -- no matter who it is, we have to win games."

So there you go. All that on the first day of the season's last month. There are 29 more to come.

Monday's key games to watch (all times ET)

White Sox (Quintana, 7-4) at Yankees (Hughes, 4-13), 1:05 p.m. Preview >
The Yankees need to win, win, win. The White Sox are seeing what they have for 2014 and beyond.

Mets (Matsuzaka, 0-2) at Braves (Maholm, 9-10), 1:10 p.m. Preview >
The Mets will see what they have in Dice-K while the Braves continue to tune up for October.

Cardinals (Wainwright, 15-8) at Reds (Latos, 13-5), 1:10 p.m. Preview >
The best pitching duel of the day -- and quite possibly the rest of the season -- should go a long way toward dictating the outcome of the packed NL Central.

Tigers (Fister, 11-7) at Red Sox (Lackey, 8-11), 1:35 p.m. Preview >
It wouldn't be a stretch to imagine this as a second-round postseason matchup. Major Comeback Player of the Year candidate Lackey has pitched better than his record indicates.

Pirates (Morton, 6-3) at Brewers (Thornburg, 1-0), 2:10 p.m. Preview >
The march to the first winning season since 1992 for the Pirates continues. Pittsburgh can nab its 80th victory here, which would mean it only needs two more to get one big monkey off its back.

Mariners (Hernandez, 12-8) at Royals (Duffy, 2-0), 2:10 p.m. Preview >
The Royals need to win just about every game they play, which will be a tough task against one of the AL's premier pitchers coming off one of his worst starts of the year.

Orioles (Norris, 9-10) at Indians (Masterson, 14-9), 4:05 p.m. Preview >
Both clubs have Wild Card hopes, which means Monday's matchup figures to be important and intense, as it should be this time of year.

Rangers (Holland, 9-6) at Athletics (Straily, 7-7), 4:05 p.m. Preview >
Here we go. The battle for the AL West is officially on, and a big series at home for the A's could do a lot for their division hopes, just like in 2012.

Blue Jays (Rogers, 3-7) at D-backs (McCarthy, 3-8), 4:10 p.m. Preview >
Arizona's postseason hopes are slim right now, but McCarthy has been better recently and can get something started with a big effort.

Nationals (Strasburg, 6-9) at Phillies (Hamels, 6-13), 7:05 p.m. Preview >
The Nationals need to beat up on sub-.500 teams like the Phillies down the stretch if they are to sneak into the postseason party. Good thing they have Strasburg on the hill here.

Rays (Archer, 8-5) at Angels (Richards, 4-6), 9:05 p.m. Preview >
Few AL starters have been better than Archer in the last few weeks. Joe Maddon's gang needs to put wins together in a hurry if it is going to challenge the Red Sox for the division title.

Magic numbers
To calculate a team's magic number, take the number of games it has remaining and add one. Then subtract the difference in the number of losses between that team and its closest pursuer.

Tiebreaker scenarios
A tiebreaker game will be played to determine a division winner, even if the tied clubs are assured of participating in the postseason. If a division championship tiebreaker is necessary, the head-to-head record between the clubs will determine home-field advantage. If the head-to-head record is tied, then division record will be the next tiebreaker.

If two clubs are tied for the two Wild Card berths, home-field advantage will be determined by the head-to-head record between the clubs. If the head-to-head record is tied, then division record will be the next tiebreaker.